feat(02-02): add thread hooks, UI store, tab navigation, and thread list

- Create useThreads/useCandidates TanStack Query hooks
- Extend uiStore with candidate panel and resolve dialog state
- Add ThreadTabs component for gear/planning tab switching
- Add ThreadCard component with candidate count and price range chips
- Refactor index.tsx to tabbed HomePage with PlanningView
- Create placeholder thread detail route for navigation target

src/client/hooks/useCandidates.ts

@@ -0,0 +1,61 @@
+import { useMutation, useQueryClient } from "@tanstack/react-query";
+import { apiPost, apiPut, apiDelete } from "../lib/api";
+import type { CreateCandidate, UpdateCandidate } from "../../shared/types";
+
+interface CandidateResponse {
+  id: number;
+  threadId: number;
+  name: string;
+  weightGrams: number | null;
+  priceCents: number | null;
+  categoryId: number;
+  notes: string | null;
+  productUrl: string | null;
+  imageFilename: string | null;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export function useCreateCandidate(threadId: number) {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: CreateCandidate & { imageFilename?: string }) =>
+      apiPost<CandidateResponse>(`/api/threads/${threadId}/candidates`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["threads", threadId] });
+      queryClient.invalidateQueries({ queryKey: ["threads"] });
+    },
+  });
+}
+
+export function useUpdateCandidate(threadId: number) {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({
+      candidateId,
+      ...data
+    }: UpdateCandidate & { candidateId: number; imageFilename?: string }) =>
+      apiPut<CandidateResponse>(
+        `/api/threads/${threadId}/candidates/${candidateId}`,
+        data,
+      ),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["threads", threadId] });
+      queryClient.invalidateQueries({ queryKey: ["threads"] });
+    },
+  });
+}
+
+export function useDeleteCandidate(threadId: number) {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (candidateId: number) =>
+      apiDelete<{ success: boolean }>(
+        `/api/threads/${threadId}/candidates/${candidateId}`,
+      ),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["threads", threadId] });
+      queryClient.invalidateQueries({ queryKey: ["threads"] });
+    },
+  });
+}